Ibrahim Omer Mohammed Ali, Bilal Naser Eldin, Osman Omran Fadl, Magzoub Magzoub Abbas
Department of Microbiology, Faculty of Medicine and Health Sciences, University of El-imam El-mahdi P.O Box 209, Kosti City, Sudan.
Department of Medical Microbiology, Faculty of Medical Laboratory Sciences, Khartoum University P.O. Box 11081, Khartoum, Sudan.
Pan Afr Med J. 2017 Aug 21;27:281. doi: 10.11604/pamj.2017.27.281.9016. eCollection 2017.
The heterogeneous expression of methicillin resistance in (MRSA) affects the efficiency of tests available to detect it. The objective of this study was to assess four phenotypic tests used to detect MRSA.
This is an analytical comparative study conducted among sudanese patients during period from May 2012 to July 2014, strains were isolated and identified by conventional methods, and then confirmed by PCR detection of coagulase gene. PCR detection of mecA gene was used as a gold standard to assess oxacillin resistance screen agar base (ORSAB), oxacillin disc, cefoxitin disc (at different temperatures and incubation periods) and MRSA-latex agglutination test. ATCC 25923 was used as control. Sensitivity and specificity were calculated.
MRSA- latex agglutination was the most accurate test; it showed 100% of both sensitivity and specificity, followed by cefoxitin disc with sensitivity of 98.48% and specificity of 100%. However, both of oxacillin disc and oxacillin resistance screen agar base showed less accurate results, and were affected by incubation periods. Oxacillin disc after 24 h incubation both at 30°C and 35°C showed sensitivity and specificity values of 87.88% and 96.23%, respectively. However, after 48h incubation the test at 30°C showed sensitivity and specificity values of 89.39%, and 94.34%, respectively. At 35°C (48h) it showed values of 89.39%, 92.45% respectively. Specificity of ORSAB was more than oxacillin disc at 35°C after 24h incubation 98.11% and 96.23%, respectively.
MRSA- latex agglutination and cefoxitin disc diffusion tests are recommended for routine detection of MRSA.
耐甲氧西林金黄色葡萄球菌（MRSA）的异质性耐药表达会影响检测其的现有测试的效率。本研究的目的是评估用于检测MRSA的四种表型测试。
这是一项在2012年5月至2014年7月期间对苏丹患者进行的分析性比较研究，菌株通过常规方法分离和鉴定，然后通过凝固酶基因的PCR检测进行确认。使用mecA基因的PCR检测作为金标准来评估苯唑西林耐药筛选琼脂基础（ORSAB）、苯唑西林纸片、头孢西丁纸片（在不同温度和孵育时间）以及MRSA乳胶凝集试验。使用ATCC 2592菌种作为对照。计算敏感性和特异性。
MRSA乳胶凝集试验是最准确的测试；其敏感性和特异性均显示为100%，其次是头孢西丁纸片，敏感性为98.48%，特异性为100%。然而，苯唑西林纸片和苯唑西林耐药筛选琼脂基础的结果准确性较低，且受孵育时间影响。苯唑西林纸片在30°C和35°C孵育24小时后，敏感性和特异性值分别为87.88%和96.23%。然而，在30°C孵育48小时后，该测试的敏感性和特异性值分别为89.39%和94.34%。在35°C（48小时）时，其值分别为89.39%、92.45%。ORSAB在35°C孵育24小时后的特异性高于苯唑西林纸片，分别为98.11%和96.23%。
推荐使用MRSA乳胶凝集试验和头孢西丁纸片扩散试验进行MRSA的常规检测。
